Lenses are commonly used in optical systems to direct and/or reconfigure light. In data communication systems, for example, lenses are used to direct and/or reconfigure light provided by a light source to a detector, optical fiber or some other destination. In many cases, the light source is provided in a light source package, and the lens is provided outside of the light source package.
To help stabilize the light beam provided by a light source, many light source packages include both a light source and a back monitor photo detector. The back monitor photo detector typically samples a portion of the light beam and provides a signal indicative of the amount of light detected by the signal path photo detector. A controller receives a signal from the back monitor photo detector, and adjusts the power of the light source to a desired, often constant, level. This can be beneficial as some electrical/optical parameters of some light sources, such as lasers, can vary due to effects such as manufacturing tolerance, temperature and aging. As such, control of the power output of light sources can enhance the performance of systems that use the light sources. It is advantageous to have a constant ratio between the response of the back monitor photo detector and the signal path photo detector.
In many cases, the back monitor photo detector and the light source are provided adjacent to one another in a common light source package. A flat tilted window, which typically includes a partially reflective coating, is often provided above the back monitor photo detector and the light source and reflects a portion of the light beam from the light source to the back monitor photo detector. A controller receives a signal from the back monitor photo detector, and provides a control signal to the light source to stabilize the output power of the light source over a range of operating conditions.
In many systems, a lens is provided outside of the light source package to help direct the light beam to a desired destination such as an optical detector, optical fiber, or some other destination. The lens can, for example, focus the light beam onto a detector, an input facet of an optical fiber, or some other desired destination.
Thus, in many optical systems, both a partially reflective window and a separate lens are provided in the path of the light beam. Having to manufacture and mount both of these separate components can increase the cost of the system. In addition, and in some application, there is insufficient room between the light source and the desired destination to accommodate both a partially reflective window and a separate lens.
What would be desirable, therefore, is a lens that includes a reflective surface. In some applications, such a lens could replace both the partially reflective window and the lens, thereby providing significant cost savings. In addition, the complexity associated with mounting both the partially reflective window and the lens could be reduced, and the size and/or spacing requirements between the light source and the desired destination may be reduced. All of these may result in more desirable optical systems.